In this June 6, 2014 file photo, grower Robert Purdy stands in his field of genetically engineered sugar beets near Salem, Oregon.

(The Associated Press)

By Fred Hiatt

Sophisticated readers know a science denier when they see one: the libertarian irresponsibly attacking vaccine safety, the oil-state senator mocking climate theory, the Southern Bible-thumper denying the fossil in front of his nose.

But the biggest gap between public opinion and scientific consensus in the United States is not in the realm of vaccines, global warming or evolution but regarding the safety of genetically modified (GM) foods. And the science deniers on this topic are more likely to be Democratic than Republican, with college-educated Americans almost evenly split.

According to a survey conducted by the Pew Research Center in association with the American Association for the Advancement of Science, 88 percent of scientists believe GM foods are safe to eat, compared with only 37 percent of the public - a gap of 51 percentage points.

An equally overwhelming majority of scientists (87 percent) believe that climate change is mostly caused by human activity, and 50 percent of the public agrees - a gap of 37 percentage points. Fully 98 percent of scientists believe that humans have evolved over time, and 65 percent of the public agrees - a gap of 33 points.

The Pew/AAAS report does not attempt to explain why so many Americans reject the scientific consensus on GM foods. It notes that educated Americans are less skeptical of the science than the public at large, but not by that much: 49 percent of people with college degrees believe eating GM foods is safe, while 47 percent believe it isn't.

The report also doesn't delve into political differences on these issues, but Lee Rainie, Pew's director of Internet, science, and technology, shared some background. On climate change, the political breakdown is what you might expect: Republicans believe by 53 to 43 percent that the evidence is real, whereas Democrats are convinced 87 to 10 percent.

On vaccine policy, there was no difference between parties when Pew asked in 2009: 68 percent thought vaccination should be mandatory, while 30 percent thought parents should decide. Since then, Rainie said, the share of Republicans favoring parental choice rose by eight points, while the share of Democrats favoring parental choice declined by five.

And on genetically modified foods?

"Declared Republicans were more likely than declared Democrats to say GM foods are generally safe - 44 percent vs. 34 percent," Rainie said in an e-mail. "But when you add those leaning towards each party to the mix, the differences between them become statistically insignificant. There are no differences on this issue among people who describe themselves as conservative, moderate, or liberal."

Could it be that in this one case the public is right and the scientists are wrong? I'd say, only if you believe Gregor Mendel was risking our health when he began playing around with pea shoots in the 1850s. A more sober analysis, from the World Resources Institute last June, granted that "genetic modifications using genes from diverse species pose a greater risk of producing unexpected effects than conventional crossbreeding," which "justifies mandatory safety studies."

But WRI concluded that "there is no evidence that GM crops have actually harmed human health" and that "food safety does not justify rejecting genetic modification outright."

The anti-GM movement seems to be fueled by a combination of anti-corporate suspicion, small-farm nostalgia and anxiety about unfamiliar technologies. It raises questions of environmental safety and corporate control as well as food safety. Some would argue that, unlike climate-change denialism or vaccine resistance, it's harmless even if baseless - who cares if Manischewitz now feels compelled to offer a line of GM-free kosher foods?

Unfortunately, this form of denialism also has victims, and they're not the folks who may choose to pay a few cents more for GM-free matzo. As the WRI paper points out, farmers need to close a 69 percent gap between the crops they produced in 2006 and the food the world will need, given population growth, by 2050.

Though far from the only solution to this challenge, genetic modification can provide seeds that are more resistant to pests, drought or disease and that produce greater yields with less water or in poorer soil. They could be, in other words, one significant component to avoiding mass hunger over the next generation. Unfortunately, resistance in rich, consuming nations discourages innovation and makes it more difficult for farmers in poor countries to adopt useful new technologies.

It's no less an affront than ever that the U.S. Senate has installed as chairman of its environment committee a man who believes that global warming is "the greatest hoax," or that a senator who is also a medical doctor would stoke unwarranted fears about vaccine safety. But the Pew survey suggests we might want to check our Whole Foods grocery carts before dialing up the outrage too high.